20W Stereo Audio Amplifier -MAX9744
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- Blue4Life
- Posts: 41
- Joined: Sat Feb 11, 2012 1:42 pm
20W Stereo Audio Amplifier -MAX9744
I wanted to know how many amps can I run the 20W Stereo Audio Amplifier -MAX9744 if I am using a 12v power supply, and if possible post a schematic for a 12v power supply
- adafruit_support_mike
- Posts: 67446
- Joined: Thu Feb 11, 2010 2:51 pm
Re: 20W Stereo Audio Amplifier -MAX9744
20W = 12v * 1.66A.
I'm afraid we don't have any designs for a 12 power supply, but there are hundreds of them online.. everything from precision battery-powered units to repurposed computer power supplies.
I'm afraid we don't have any designs for a 12 power supply, but there are hundreds of them online.. everything from precision battery-powered units to repurposed computer power supplies.
- Blue4Life
- Posts: 41
- Joined: Sat Feb 11, 2012 1:42 pm
Re: 20W Stereo Audio Amplifier -MAX9744
Isn't that too high? I feel it would burn the board if I run it that high.
- adafruit_support_mike
- Posts: 67446
- Joined: Thu Feb 11, 2010 2:51 pm
Re: 20W Stereo Audio Amplifier -MAX9744
Nope. The board is designed for 20W output with supply voltages up to 14v.
- Blue4Life
- Posts: 41
- Joined: Sat Feb 11, 2012 1:42 pm
Re: 20W Stereo Audio Amplifier -MAX9744
What would happen if I run it on 12v 2amps?
- adafruit_support_mike
- Posts: 67446
- Joined: Thu Feb 11, 2010 2:51 pm
Re: 20W Stereo Audio Amplifier -MAX9744
In general, electronic devices use however much current they need at a given voltage.
A 12v @ 2A power supply is able to keep up with devices that want 2A when their supply voltage is 12v, but that's all. It won't push 2A through a device that wants less. The MAX9744 wants about 1.6A when the supply voltage is 12v, so that's all it will pull from the power supply.
A 12v @ 2A power supply is able to keep up with devices that want 2A when their supply voltage is 12v, but that's all. It won't push 2A through a device that wants less. The MAX9744 wants about 1.6A when the supply voltage is 12v, so that's all it will pull from the power supply.
- Blue4Life
- Posts: 41
- Joined: Sat Feb 11, 2012 1:42 pm
Re: 20W Stereo Audio Amplifier -MAX9744
Thanks for the help
- gbuggy79
- Posts: 5
- Joined: Fri Apr 17, 2015 7:55 pm
Re: 20W Stereo Audio Amplifier -MAX9744
I have this amplifier and I have it hooked up to 20W 4Ohm speakers (also purchased from Adafruit). When I power it with my digital power supply at 12V, it never draws more than 80mA, and the audio is a lot quieter than I'd expect 20W to be. The volume pot is turned all the way up, and the audio file I amp playing is even normalized to nearly 200%. My power supply is set to 12V and the Amp limit is set to 2.0.
So it seems like it is putting out less than a watt through the speakers: 12v * 0.08A * 0.93efficiency = 0.89W
Am I doing something wrong?
So it seems like it is putting out less than a watt through the speakers: 12v * 0.08A * 0.93efficiency = 0.89W
Am I doing something wrong?
- adafruit_support_mike
- Posts: 67446
- Joined: Thu Feb 11, 2010 2:51 pm
Re: 20W Stereo Audio Amplifier -MAX9744
Post a photo showing your hardware and connections (800x600 images usually work best) and we'll take a look.
- gbuggy79
- Posts: 5
- Joined: Fri Apr 17, 2015 7:55 pm
Re: 20W Stereo Audio Amplifier -MAX9744
Here are some pics of my test rig.
I figured out how to set the volume on the Raspberry Pi that I am sourcing the signal from, and it is much louder, but it still isn't drawing anywhere near 20W of power.
I used the command 'amixer set PCM -- 0400' to set the Pi's volume to 100%
I took a video of the power supply in action: https://www.youtube.com/watch?v=D71G3sbgLaI
Right at the beginning of the guitar solo (0:17), you can see the power spike to 1.07A/12.8W, but you can see that it usually stays below 10W.
I figured out how to set the volume on the Raspberry Pi that I am sourcing the signal from, and it is much louder, but it still isn't drawing anywhere near 20W of power.
I used the command 'amixer set PCM -- 0400' to set the Pi's volume to 100%
I took a video of the power supply in action: https://www.youtube.com/watch?v=D71G3sbgLaI
Right at the beginning of the guitar solo (0:17), you can see the power spike to 1.07A/12.8W, but you can see that it usually stays below 10W.
- adafruit_support_mike
- Posts: 67446
- Joined: Thu Feb 11, 2010 2:51 pm
Re: 20W Stereo Audio Amplifier -MAX9744
There are a couple of things that could be involved.
First, we're still not sure how much actual voltage swing you're getting out of the RasPi. It might be putting out standard line voltage, which is around +/-1v. That's still kind of low by the MAX9744's terms.
Second, it looks like your power supply is using the same kind of ciruit used in multimeters.. most likely a dual-slope measurement. Those give good results, but they're slow. It looks like yours updates about four times per second, which isn't fast enough to catch the highs and lows of a complex audio signal.
To measure the true peak current you'd need an oscilloscope or a moderately complicated peak-tracking circuit and a sense resistor.
First, we're still not sure how much actual voltage swing you're getting out of the RasPi. It might be putting out standard line voltage, which is around +/-1v. That's still kind of low by the MAX9744's terms.
Second, it looks like your power supply is using the same kind of ciruit used in multimeters.. most likely a dual-slope measurement. Those give good results, but they're slow. It looks like yours updates about four times per second, which isn't fast enough to catch the highs and lows of a complex audio signal.
To measure the true peak current you'd need an oscilloscope or a moderately complicated peak-tracking circuit and a sense resistor.
Please be positive and constructive with your questions and comments.